Trace Email Research and Scenario for Assignment

[InvestigatorDude]

Hello all! I am a student and have been tasked with doing research on methods for tracing email info. The scenario is that someone has been sending threatening messages to a victim using an anonymous email service to the victims personal gmail or other email account. The device used was a portable device like an ipad or samsung galaxy connected to a free wifi service like McDonalds or a Library.

We are supposed to research methods and resources that could be used, even using the legal system such as subpoenas, as to how to trace the emails to a location and device.(even though they are using anonymous service) We are supposed to research if the actual MAC address of the device can be found through email services.

Any keywords, tools, resources, answers,info, comments for my research are greatly appreciated. I am thinking on can't get the MAC address of the device from the scenario. Also, the fact an anonymous email service was used, maybe even more difficult.
This post is part of my research.
Thanks.

I also am researching if using the Tor Network or Tails software on a USB drive to boot the computer from, would make it impossible. It was something we discussed in class, but not indepth.
I go to ITT currently.
Course is Computer Forensics: Evidence Collection and Preservation